function binarySearch(arr,target){
    let left:number = 0;
    let right:number = arr.length -1;

    while(left <= right){
        let mid = Math.floor((left+right)/2);
        if(arr[mid] === target){
            // find target,查找解释
            // break 
            return
        }else if(arr[mid] < target){
            left = mid +1;
        }else {
            right = mid -1;
        }
    }
}
